One component organopolysiloxane compositions which can be stored with exclusion of moisture and crosslink at room temperature on admission of moisture, known as RTV-1 compositions, have been known for a long time.
In the preparation of the RTV-1 compositions, not all constituents can be added in one step; rather, after mixing part of the constituents, a certain reaction time is necessary before further constituents are mixed in. Two-stage processes have been developed for this purpose. For example, in EP-A-234 226, part of the constituents are combined in a first step in a continuous closed mixer, and in a second step in a reciprocating kneader, the remaining constituents are metered in and the composition is homogenized and degassed under reduced pressure in this kneader.
RTV-1 compositions are compounded to form many different products for various applications which differ, for example, in terms of color, transparency or viscosity. In the process of EP-A-234 226, when the product is changed, for example in the case of a color change, the entire reciprocating kneader has to be cleaned or at least generously purged with the composition according to the changed formulation. This is associated with large product losses.